Image covering laminate film and image projection sheet

ABSTRACT

The laminate film for covering of an image carried by a support has a construction comprising a transparent base material and a transparent adhesive layer formed on one side of the base material, wherein the adhesive layer is composed of a pressure-sensitive adhesive and has a surface with a fine uneven structure.

TECHNICAL FIELD

The present invention relates to a laminate film. In particular, itrelates to a laminate film useful for protecting images such as tonerimages on transparent sheets.

BACKGROUND

Transparency sheets for image projection usually comprise a transparentplastic film as the support, with a monochrome or color image formed bytoner fusion carried as an image on one surface thereof. The toner isgenerally composed of a binder resin such as polyester resin, a coloringagent (dye or pigment) and a static control agent. The toner is usuallyused to form a toner image with an electrophotographic system.

In the past, several problems have arisen when transparency sheets arefabricated by forming color images on overhead projector (OHP)transparent films with color copiers or printers employingelectrophotographic systems. One of these problems has been insufficientmelting of the color toner in the transparent film, resulting inresidual uneven sections in the toner image layer. When uneven sectionsare present in the toner image layer it is difficult to avoid scatteringof transmitted light, and this causes considerable reduction in thequality of the projected color image at the stage in which thetransparency sheet is actually used in an OHP.

One known method of preventing undesirable light scattering on thesurface of the toner image layer is to cover the toner image layer ofthe transparency sheet with a transparent film. That is, it has beenproposed to cover the toner image layer with a transparent film so thatthe uneven sections of the toner image layer are buried and flattened bythe transparent adhesive of the film and scattering of transmitted lightis thereby reduced.

More specifically, Japanese Unexamined Patent Publication (Kokai) No.2-38090, for example, discloses an image covering method characterizedin that, after a toner image is formed on the transparent film, a coversheet comprising a film and/or paper/release agent layer/thermoplastictransparent resin layer is combined with the toner image side of thefilm from the thermoplastic transparent resin layer side of the coversheet, and the laminate is subjected to heating and pressure on a rolleror plate, the thermoplastic transparent resin is cooled, and then thefilm and/or paper is released.

With this image covering method and other film covering methods,however, during the hand lamination when the covering sheet or film ismanually combined with the color image side of an OHP transparent film,air becomes entrapped between the transparent film and the coveringsheet or film, creating a new problem of residual air bubbles. Once airbubbles have been trapped, they are difficult to remove even using atool such as a squeegee. When air bubbles reside on the color image sideof the transparency sheet, they not only reduce the adhesion performancebut also cast their shadows which are reproduced as image defects in theprojected image, thus impairing the quality of the projected image.

Moreover, a high level of skill can be required for hand laminatingcovering sheets or films for OHP transparent films. In the case ofconventional hand lamination, strong adhesive force is present from theadhesive layer when the covering sheet or film is attached to the OHPtransparent film, and the resulting difficulty in achieving adequatepositioning often leads to attachment in the wrong position.Reattachment after attachment in the wrong position is very difficult inmost cases, and can damage the image sides of transparent films. Thus,there has been a need to provide covering sheets or films, particularlyfor OHP transparent films, that can be easily and precisely positionedand that can also be easily reattached after attachment in a wrongposition.

Referring again to the image covering method described in JapaneseUnexamined Patent Publication (Kokai) No. 2-38090, this method requiresheat and pressure treatment using special means during lamination. Theoperation is complicated, the production costs are likely increased, andother problems also occur such as heat deformation of the transparentfilm or covering sheet during heating.

Difficult storage and filing has been another problem associated withconventional OHP transparency sheets. For example, when preparedtransparency sheets are compiled in a binder or the like for storage, ithas been necessary to perforate the edges of the transparency sheets,insert each of the transparency sheets into a specialized perforatedholder and the close the binder.

SUMMARY

In light of the aforementioned problems of the prior art, the presentinvention provides an image covering laminate film that can be handlaminated at room temperature and attached onto OHP transparent films.The invention also provides an image covering laminate film thatimproves the storage and filing properties of OHP transparency sheets.

The laminate film of the invention is laminated onto the image-bearingside of transparent sheets. It may be hand laminated at room temperaturewithout requiring special lamination equipment or skills. Handlamination can be done using a small rubber roller. The inventivelaminate film prevents air entrapment that can cause air bubbles duringlamination. Even if air bubbles are incorporated, the laminate filmallows them to be easily forced outside. Yet the laminate film alsoexhibits satisfactory slidability on the surface of the transparentsheet to facilitate the positioning and attachment operations. Theinventive laminate film can also enhance the quality of projected imagesbecause uneven sections generated from the toner image on the surface ofthe transparent sheet are buried in the adhesive layer thus producing aflattened image layer. As a result, scattering of transmitted light canbe reduced. The invention further relates to an image projection sheetprovided with a laminate film of this type. Typical image projectionsheets are laminated transparency sheets used for overhead projectors(OHPs).

In one aspect, the present invention provides an image covering laminatefilm for covering of an image carried by a support (hereunder alsoreferred to as “image-carrying support” or “adherend”), the laminatefilm being characterized in that it comprises a transparent basematerial and a transparent adhesive layer formed on one side of the basematerial, and the adhesive layer is composed of a pressure-sensitiveadhesive and has a surface with a fine uneven structure.

In another aspect, the invention provides an image projection sheetcomprising a transparent support and a toner image carried on thesurface of the support, the image projection sheet being characterizedin that a laminate film comprising a transparent base material and atransparent adhesive layer formed on one side of the base materialcovers the image-bearing side of the support via the adhesive layer, andthe adhesive layer is composed of a pressure-sensitive adhesive and hasa surface with a fine uneven structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described with reference to the followingfigures.

FIG. 1 is a cross-sectional view showing a preferred embodiment of animage covering laminate film according to the invention.

FIG. 2 is a cross-sectional view showing the construction of theadhesive layer of the laminate film of FIG. 1.

FIG. 3 is a plan view showing the construction of the adhesive layer ofFIG. 2.

FIG. 4 is a cross-sectional view showing the construction of theadhesive layer of a laminate film of the invention in which fineparticles are embedded.

FIG. 5 is a plan view showing the construction of the adhesive layer ofFIG. 4.

FIG. 6 is a cross-sectional view showing the construction of theadhesive layer of a laminate film according to the invention.

FIG. 7 is a plan view showing the construction of the adhesive layer ofFIG. 6.

FIG. 8 is a cross-sectional view showing the dimensions of the adhesivelayer of FIG. 6.

FIG. 9 is a perspective view showing examples of protrusions that may beadded to a laminate film according to the invention.

FIG. 10 is a cross-sectional view showing the dimensions of an adhesivelayer provided with the type of protrusion shown in FIG. 9(C).

FIG. 11 is a cross-sectional view showing the construction of astrip-attached laminate film according to the invention.

FIG. 12 is a plan view showing the construction of the strip of thelaminate film of FIG. 11.

FIG. 13 is cross-sectional view showing a preferred embodiment of animage projection sheet according to the invention.

FIG. 14 is a graph showing a light transmittance curve for the redimage-bearing transparency sheet fabricated in Example 2.

FIG. 15 is a graph showing a light transmittance curve for the greenimage-bearing transparency sheet fabricated in Example 2.

FIG. 16 is a graph showing a light transmittance curve for the blueimage-bearing transparency sheet fabricated in Example 2.

FIG. 17 is a graph showing a light transmittance curve for the yellowimage-bearing transparency sheet fabricated in Example 2.

The figures are idealized, not drawn to scale, and are intended merelyto be illustrative and non-limiting.

DETAILED DESCRIPTION

An image covering laminate film and image projection sheet according tothe invention will now be described in detail.

The laminate film of the invention will typically serve as a coveringfor an image carried by a support. The laminate film comprises atransparent base material and a transparent adhesive layer formed on oneside of the base material. The transparent adhesive layer is notparticularly restricted so long as it satisfies the conditions mentionedabove and described below in detail.

Considering that the effect of the laminate film of the invention issatisfactorily exhibited and light scattering can be preventedparticularly when the image is a monochrome or color image, it is mostsuitable for covering of color toner images. The toner image formingmethod is not particularly restricted and includes, for example, anymethod based on an electrophotographic system (electrophotography,electrography, ionography, etc.) that is widely used in the art of imageformation. Such image forming methods are described in detail in thepatent literature and related documents and will therefore not berepeated here. As will be explained below, the inventive laminate filmis particularly useful for covering of OHP transparency sheets, but, ifdesired, it may be used to enhance or protect the quality of tonerimage-bearing elements or photographic prints.

FIG. 1 is a cross-sectional view showing a preferred embodiment of animage covering laminate film according to the invention. The laminatefilm 10 includes a transparent base material 1 and a transparentadhesive layer 2 that is attachable to the image-bearing side of animage carrying support such as an OHP transparent film (not shown). Thesurface of the adhesive layer 2 has a fine uneven structure. Theadhesive layer 2 is typically covered with a release liner 3 to protectit until use of the laminate film. In order to form a fine unevenstructure, which preferably is a combination of protrusions andcontinuous grooves, to the surface of the adhesive layer 2, the surfaceof the release liner 3 is preferably provided with depressions andcontinuous fine protrusions at corresponding positions. While not shownhere, the laminate film 10 may also have an additional layer ifnecessary. The adhesive layer 2 is preferably a pressure-sensitiveadhesive, and is preferably non-repositionable. By using apressure-sensitive adhesive it is possible to achieve firm adhesionbetween the laminate film and the adherend.

The fine uneven structure of the surface of the adhesive layer 2functions to expel out air trapped between the laminate film and theimage-bearing side of the image carrying support when the former isattached to the latter. The uneven structure preferably has a shape anddimensions allowing it to be incorporated into the adhesive layer and todisappear once the attachment is complete. A suitable uneven structureis a group of protrusions dispersed regularly or at random andcontinuous grooves formed between the protrusions.

Protrusions and continuous grooves may be used in various combinationsto form the uneven structure in the surface of the adhesive layer.Specifically, these two elements may be provided by protrusions ofvarious shapes and sizes for optimum control to maximize their effect.The protrusions may be arranged in either a regular pattern or a randompattern. For example, the protrusions may have a regular pyramidal,triangular pyramidal, conal, truncated pyramidal, truncated conal,hemispherical or spherical shape, with any desired combination ofprotrusions being used depending on the case. Among these groups ofprotrusions, the border sections between adjacent protrusions willnormally be lower than the other sections of the protrusions, andtherefore continuous grooves according to the invention may thus beformed.

FIG. 2 and FIG. 3 are, respectively, a cross-sectional view and planview of a preferred embodiment of a fine uneven structure for a laminatefilm according to the invention. As shown here, the fine unevenstructure 12 is constructed so that the regular pyramidal protrusions 26are positioned at equal spacings on the surface of the adhesive layer 2,which is coated on the surface of the transparent base material 1.V-shaped continuous grooves 24 in a lattice pattern between each of theprotrusions 26. As a result of the arrangement of the protrusions 26 andcontinuous grooves 24, it is possible to simultaneously improve the airremovability and the slidability, and the dense arrangement ofprotrusions also improves the attachment manageability and preventsreduced light transmittance. The improved air removability also allowslamination to be carried out at room temperature without any speciallamination equipment or skills.

Other laminate films according to the invention can usually be appliedin the same manner, but the laminate film illustrated in FIG. 2 and FIG.3 preferably has the group of protrusions 26 formed on the surface ofthe adhesive layer 2 at a pitch p (average value of the distance betweencenters of adjacent protrusions 26) of no greater than 400 μm. If thepitch p between protrusions is greater than 400 μm, a pattern ofprotrusions may appear on the surface of the laminate film afterattachment, resulting in reduced quality of the projected image. Theheight h of the protrusions 26 as measured from the bottom of thecontinuous grooves 24 is preferably in the range of 3-30 μm. If theheight h of the protrusions 26 is less than 3 μm the air removability isnot exhibited, while if it is greater than 30 μm the quality of theprojected image is likely to be impaired. The length of the long sidesof the continuous grooves 24 is preferably from 1 μm to the size of thepitch p. If the length is less than 1 μm, the air removability is notlikely exhibited. Considering the construction of the continuousgrooves, the length of the long sides will never be longer than thepitch.

The surface of the adhesive layer in the image covering laminate film ofthe invention preferably also contains fine particles, and the fineparticles are preferably non-adhesive. As will be explained in detailbelow, the presence of such fine particles can contribute to furtherimproved positionability and slidability for the lamination treatment.

FIG. 4 and FIG. 5 are, respectively, a cross-sectional view and planview of an embodiment wherein fine particles 4 are embedded in thesurface of the adhesive layer 2 of the laminate film. As shown in theseillustrations, the fine uneven structure 12 contains fine particles 4composed of glass beads in the slanted surface of the regular pyramidalprotrusions 26. Each of the fine particles 4 is anchored with celluloseresin. In the embodiment shown here, one fine particle 4 is embedded ineach protrusion 26, but the number of fine particles 4 may be two ormore as necessary. Depending on the need, some of the protrusions 26 maybe free of embedded fine particles 4. The fine particles 4 arecylindrical in these illustrations, but they may have the same ordifferent shapes and dimensions.

In the laminate film shown in FIG. 4 and FIG. 5, the group ofprotrusions 26 dispersed on the surface of the adhesive layer 2 ispreferably formed with a pitch p₁ (average value of the distance betweencenters of adjacent protrusions 26) of no greater than 400 μm, asexplained above. The height h₁ of each of the protrusions 26 from thebottoms of the continuous grooves 24 is preferably in the range of 3-30μm. In most cases, the fine particles 4 embedded in the protrusions 26will preferably have a diameter d of about 1-100 μm, a pitch p₂ (averagevalue of the distance between adjacent fine particles 4) of no greaterthan 400 μm and a height h₂ (height of each of the fine particles 4 fromthe bottoms of the continuous grooves 24) of about 5-50 μm.

FIG. 6 and FIG. 7 are, respectively, a cross-sectional view and planview of another preferred embodiment of a fine uneven structure in alaminate film according to is the invention. As shown in theseillustrations, the fine uneven structure 12 is constructed so thattruncated pyramidal (or trapezoidal) protrusions 36 are situated atequal spacings on the surface of the adhesive layer 2 coated on thesurface of the transparent base material 1, with inverted trapezoidalcontinuous grooves 34 running in a lattice pattern between each of theprotrusions 36. As a result of the arrangement of the protrusions 36 andcontinuous grooves 34 in this pattern, it is possible, as with theembodiment described above, to simultaneously improve the airremovability and the slidability, and the dense arrangement ofprotrusions also improves the attachment manageability and preventsreduced light transmittance.

The uneven structure of the laminate film illustrated in FIG. 6 and FIG.7 may have the following dimensions, for example, based on FIG. 8. Thepitch between adjacent protrusion is less than 400 μm; the height ofeach protrusion is about 3-30 μm, as measured from the bottom of thecontinuous groove, the width (d₁) of the base of the continuous grooveis from 0 μm to a size adequate for a base angle α of 1-90°; and thewidth (d₂) of the continuous groove is from 1 μm to the size of thepitch.

As mentioned above, various modifications may be made to the protrusionsin order to form a finer uneven structure. FIG. 9 shows schematic viewsof three different protrusion embodiments that may be used in thisinvention. The protrusions shown here will be referred to as “doublemechanism structures” for the purpose of the present invention. Bystacking two structures, it is possible to further reduce the initialcontact surface of the adhesive and reinforce the positionabilityimparted to the laminate film. FIG. 9(A) shows a truncated pyramid 42with an exposed surface 43. A second pyramid 44 with a base 45 issituated on the exposed surface 43. FIG. 9(B) shows another embodimentof a double mechanism structure according to the invention. Arectangular mechanism 46 provides a base surface 47 which receives thebase 49 of a second smaller rectangular mechanism 48. In most cases, thesurface of the base of the second structure will generally be smallerthan the exposed surface of the first mechanism. In order to achievepreferred positioning properties for the invention, differentarrangements and shapes may be combined with the basic structure. FIG.9(C) is a modification of the double mechanism structure shown in FIG.9(A). The protrusions shown here consist of a truncated pyramid 42 withan exposed surface 43, wherein a pyramid 41 having a base 45 is providedon the exposed surface 43.

As further explanation, the uneven structure of the laminate film withprotrusions as shown in FIG. 9(C) may have the following dimensions, forexample, based on FIG. 10. The pitch between adjacent protrusions isless than 400 μm; the height h is about 30-30 μm; the height hi is about1-25 μm; the height h₂ is about 1-20 μm; the base width d₁ of continuousgrooves is from 0 μm to size adequate for a base angle α₁ of 1-90°; topwidth d₂ of continuous grooves is from 0 μm to size adequate for a baseangle α₁ of 1-90° and a base angle α₂ of 1-90°; and the base side d₃ ofpyramid 41 is from 0 μm to size adequate for a base angle α₂ of 1-90°.

When the inventive laminate film is used to store and file OHPtransparencies, it is preferably constructed with a strip which extendsout from one edge. The strip may be laid by any of several methods, butit is particularly preferred to form the strip by designing the edge ofthe transparent base material of the laminate film to extend at aprescribed length from the edge of the laminate film, or to fabricate astrip separately from the laminate film and attach the strip to the edgeof the laminate film at the desired stage.

FIG. 11 and FIG. 12 show a preferred embodiment of a laminate film witha strip. The laminate film 10 shown here is based on the laminate filmexplained above with reference to FIG. 1, and therefore comprises atransparent base material 1 and a transparent adhesive layer 2 andrelease liner 3. As shown in these illustrations, one of the edges ofthe base material 1 extends out at a prescribed length to form a strip5. Small holes 6 are formed at predetermined positions in the strip 5.The small holes 6 can be advantageously used to file the laminate film10 (or an image projection sheet fabricated using it) in a binder or thelike. Thus, the holes 6 may be formed in any desired number and sizesdepending on the intended use of the laminate film. The strip 5 may, ofcourse, be formed without holes if desired.

As mentioned above, the laminate film of the invention possesses variousconstructions and features within the scope of the invention. Theconstructions and features of the laminate film of the invention willnow be explained in further detail.

The transparent base material may be constructed of any of severalplastic materials that are commonly used in the technical field.Examples of suitable base materials include, but are not limited to,polyester resin, polystyrene resin, polycarbonate resin, vinyl resin,polyvinyl chloride resin, plasticized polyvinyl chloride resin,polyurethane resin, polyethylene resin, polypropylene resin, fluorineresin and the like. A particularly preferred plastic base material forcarrying out the invention is polyethylene terephthalate (PEI). Thisresin is preferred because of its excellent transparency, strength andrigidity. The thickness of the base material may vary widely dependingon the intended use, but will generally be about 300 μm or less, andpreferably in a range of about 25-100 μm.

The base material may be subjected to primer treatment if desired toincrease the adhesion between the base material and the adhesive layerformed on it.

The exposed, ie., non-adhesive side, of the base material may contain animage or print. A more unique projection effect is achieved byprojecting a pattern (e.g., a background) derived from a print, incombination with the image projection. In general, the surface will becovered with a clear layer after an ink layer has been formed to producethe desired print. Both the ink layer and the clear layer may be formedusing common techniques used for production of marking films.

The adhesive layer of the inventive laminate film is not particularlyrestricted so long as the prescribed level of transparency is ensured. Apressure-sensitive adhesive is preferably used. The pressure-sensitiveadhesive is also preferably non-repositionable. Pressure-sensitiveadhesives useful for formation of the adhesive layer include, but arenot limited to, the following: polyacrylate, tackifying rubber,tackifying synthetic rubber, ethylene-vinyl acetate, silicone, and thelike. Acrylic-based adhesives suitable for carrying out the inventionare disclosed, for example, in U.S. Pat. Nos. 3,239,478, 4,181,752,4,952,650, 5,169,727 and Reissued Pat. No. 24,906. Preferredpressure-sensitive adhesive classifications are allyl acrylatehomopolymers and copolymers, and their poly copolymers.

An adhesive may be, e.g., a polymer coated and dried onto the releaseliner after dispersion in a solvent or water, and it may also becrosslinked. If a solvent-based or aqueous pressure-sensitive adhesivecomposition is used, the adhesive layer may be subjected to a dryingstep to remove all or most of the solvent or water. The adhesive mayalternatively be a hot melt adhesive. A low molecular polymerizableadhesive composition may also be coated onto the release liner andpolymerized or crosslinked by heating, UV irradiation, electron beamirradiation or the like.

The adhesive may also contain one or more different additives ifnecessary. Depending on the polymerization method, application methodand final use, additives such as initiators, crosslinking agents,plasticizers, tackifiers, chain transfer agents, antioxidants,stabilizers, flame retardants, viscosity reinforcers and the like, ormixtures thereof, may be used.

The thickness of the adhesive layer may be varied within a wide rangedepending on numerous factors including the composition of the adhesive,the shapes and dimensions of the protrusions and continuous grooves, thetype of adherend and the thickness of the base material. The thicknessof the adhesive layer is generally preferred to be in the range of about10-100 μm.

As mentioned above, a plurality of protrusions are dispersed in thesurface of the adhesive layer to form the fine uneven structure, and ifnecessary at least one fine particle may be provided on the surface ofthe each protrusion. The shape of the protrusions is not particularlyrestricted. Since the fine particles are optional, the protrusions maycontain no fine particles or only some of the protrusions may containfine particles. The fine particles are preferably non-adhesive.

The material and shape of the fine particles provided on the surface ofthe protrusions are not particularly restricted so long as they are ableto contribute satisfactory slidability to the laminate film on theadherend, such as an OHP transparent film. However, the fine particlespreferably have a substantially spherical or nearly spherical shape inorder to achieve satisfactory slidability. Glass beads are particularlyeffective for carrying out the invention because they can be producedeconomically to substantially uniform dimensions. Other useful fineparticles include ceramic particles, metal particles and polymerparticles. If necessary, electrical conductive particles or fine spheresof an adhesive may be used.

The size of the fine particles may be varied within a wide range.However, in order to avoid reduced slidability, to avoid damage to thebase material, and to avoid reduced light transmittance of the resultinglaminate film, the size of the fine particles is preferably no greaterthan the thickness of the adhesive layer in which they are provided. Thesize of the fine particles will usually be in a range of about 1-100 μmin terms of the average diameter. For an adhesive layer thickness ofapproximately 25 μm, an average diameter of less than about 20 μm ispreferred, with the range of about 5-15 μm being more preferred.

In addition to the protrusions described above in the adhesive layer ofthe laminate film, fine continuous grooves are also formed between eachprotrusion, being limited by the peripheral edges of the adhesive layer.The continuous grooves are extremely fine, and their presence typicallycannot be observed by the naked eye. That is because the continuousgrooves cannot be clearly seen by visual observation from any plane,they are of a fineness which can only be observed microscopically. W. J.Smith in Modem Optic Engineering, pp. 104-105, published 1966 byMcGraw-Hill Co. states that vision is “defined and measured as thevisual angle size of the smallest character that can be distinguished”.Normal vision is considered to be that where the smallestdistinguishable character forms an arc with an angular height of 5minutes on the retina. For a typical observation distance of 250 mm (10inches), this would be a lateral distance of 0.36 mm (0.0145 inch) ofthe distinguished object.

The continuous grooves formed in the adhesive layer, while being finelyformed, functions to expel out air trapped between the laminate film andthe adherend (such as an OHP transparent film) when the former isattached to the latter (“air removal”). Once attachment of the laminatefilm has been completed, the continuous grooves themselves disappear bybeing incorporated into the adhesive layer, thus eliminating any adverseeffect the continuous grooves may have on light transmittance.

The shapes and dimensions of the continuous grooves are not particularlyrestricted so long as the aforementioned function and effect areachieved. For example, although the continuous grooves may have variousmodifications depending on the working method used, they preferably havea V-shaped, U-shaped, rectangular or inverted trapezoidal shape whenviewed in the cross-sectional direction. The limit to the dimensions ofthe continuous grooves may be explained in terms of the aspect ratio.The aspect ratio is defined as the ratio between the maximum microscopicdimension of the continuous groove in the direction parallel to theplane of the adhesive layer and the maximum microscopic dimension of thecontinuous groove in the direction perpendicular to the plane of theadhesive layer. The aspect ratio can be measured by determining thecross-sectional dimensions of the continuous groove at an angleperpendicular to the wall of the groove. The limit to the aspect ratiowill vary depending on the type of continuous groove, but will normallybe in the range of about 0.1-20, and preferably in the range of about10-15.

The continuous grooves can be formed on the surface of the adhesivelayer in a variety of different patterns. The continuous grooves may bearranged in random, or in a regular pattern. The “pattern” of thecontinuous grooves includes primarily linear patterns and primarilycurved patterns. A plurality of different groove patterns may also becombined to form one connected continuous groove pattern on the surfaceof the adhesive layer.

The continuous grooves are preferably formed as continuous fineprotrusions on the surface of the release liner facing the adhesivelayer and may be formed by covering the adhesive layer therewith. Thus,the fine protrusions of the release liner may have a shape interlockingwith the continuous grooves, and specifically may have a triangular,inverted U-shaped, rectangular or trapezoidal cross-section.

The total thickness of the laminate film of the invention (ie., the sumof the thicknesses of the base material and the adhesive layer, and alsoincluding the thicknesses of any additional layers if present) may varywidely depending on the particular laminate film, but is usuallypreferred to be in the range of about 50-300 μm.

The release liner may be constructed in any of a variety of forms. Therelease liner preferably contains depressions and continuous fineprotrusions on its surface, while the depressions and fine protrusionsare preferably of a form corresponding to the shapes and dimensions ofthe protrusions and continuous grooves required for the adhesive layerof the intended laminate film.

The release liner may be constructed from a variety of base materials.The most suitable base materials are paper or plastic materials, such aspolyethylene resin, polypropylene resin, polyester resin, celluloseacetate resin, polyvinyl chloride resin, polyvinylidene fluoride resinor the like. Paper or another material that has been coated or laminatedwith plastic materials can also be used. Embossable coated paper orthermoplastic films may be used directly, but they are preferably usedafter silicone treatment or treatment by other methods to improve therelease properties. The thickness of the release liner will differconsiderably depending on the desired effect. The thickness of therelease liner is usually preferred to be in the range of about 30-300μm. A desired structure can be formed in the release liner using thevarious techniques disclosed in U.S. Pat. No. 5,650,215.

Depressions and fine protrusions can be created in the release linerusing various techniques including embossing. A specialized master toolusing the microrib location technique developed by the present applicantis preferably used to transfer its pattern to the surface of the releaseliner.

The laminate film of the invention may be produced using any of variouscommonly used techniques. It may be produced by any combination of thefollowing processing steps.

(1) A step of forming a plurality of fine depressions in a predeterminedpattern on the surface of the release liner that is to be adhered to theadhesive layer of the laminate film. For example, one useful releaseliner for this purpose is a “polycoat liner” which has a polyethylenecoating formed on both sides of a paper base material. A polyester basematerial may be used instead of a paper base material. One of thepolyethylene coatings of the release liner is coated with a siliconesolution for release treatment. Depressions are then formed in thesilicone treated polyethylene coating by embossing. The embossing may beaccomplished, e.g., by pressure rolling the polyethylene coating on oneside of the release liner using an emboss roll known as a “master tool”.The depressions may alternatively be formed in the release liner byanother type of mechanical working or etching treatment instead ofembossing with a master tool.

(2) An optional step of filling at least one fine particle into each ofthe depressions formed in step (1). For example, fine particles (such asglass bead clusters) are filled into the depressions formed in theprevious step, usually in such a manner as to be completely embedded inthe depressions, in order to improve the slidability. For filling ofglass beads, the glass beads are preferably dispersed in a celluloseresin to obtain a slurry solution which is then coated over the entiretyof the release liner surface.

(3) A step of raking off the excess fine particles not filled in thedepressions using a doctor plate, for example, when fine particles areused. Air blasting may be used instead of a doctor plate.

(4) A step of creating a fine structured surface comprising continuouslyformed fine protrusions on the surface of the release liner providedwith depressions (filled with fine particles depending on the case). Forexample, fine protrusions are formed by reembossing on the polyethylenecoating of the release liner. The embossing may be accomplished by themethod described above, or by another method depending on the case. Thesurface pattern of the emboss roll is transferred to the polyethylenecoating to obtain a release liner with fine protrusions.

(5) A step of coating a pressure-sensitive adhesive onto the finestructured surface of the release liner to a thickness sufficient tocompletely cover the fine structured surface, to form an adhesive layer.For example, a selected pressure-sensitive adhesive is applied to aprescribed thickness onto the polyethylene coating of the release linerwith fine protrusions, and then dried and cured. The pressure-sensitiveadhesive may be applied using a common coating method such as barcoating.

(6) A step of laminating a base material for the laminate film onto theadhesive layer of the release liner to complete the intended laminatefilm. For example, a laminate film base material is laminated afterforming the adhesive layer on the release liner. The base material maybe laminated by a common laminating method using a pressure roller orthe like.

As mentioned above, these steps may be carried out in a different orderif necessary, and additional steps may also be carried out depending onthe desired construction for the laminate film.

The image covering laminate film of the invention may be used in avariety of technical fields to take advantage of its excellentproperties, but it may be used with particular advantages for productionof image projection sheets. The types of image projection sheets thatare especially useful are OHP transparency sheets having images formedby toner fusion. That is, while images can also be formed by ink-jetprinting methods for production of image projection sheets, it is mostadvantageous for carrying out the invention to form images using toneras the coloring material. The toner image forming method is notparticularly restricted, and an electrophotographic method is a typicalexample. More specifically, OHP transparency sheets with toner imagesmay be advantageously produced by using, for example, a widely availablecolor laser beam printer (CLBP) for fusion of the color toner image ontoa specialized transparent film.

FIG. 13 shows an OHP laminated transparency sheet as a preferredembodiment of an image projection sheet according to the invention. Thelaminated transparency sheet 20 has a toner image 15 on the surface of atransparent support (OHP transparent film) 11, and the side of thesupport 11 containing the toner image 15 is covered with a laminate film10 according to the invention, through an adhesive layer 2. As a resultof covering the toner image 15 with the laminate film 10, the surface ofthe toner image 15 is flattened so that inconveniences such as inclusionof air bubbles are eliminated.

In the image projection sheet of the invention, the support carrying thetoner image may be formed of any material so long as it is transparentand causes no adverse effect on the image projection. Considering lighttransmittance, manageability and cost, it is most advantageous to formthe support of a plastic material. Suitable plastic materials include,but are not limited to, polyester resin, polypropylene resin, polyvinylchloride resin, polyurethane resin, polystyrene resin, polycarbonateresin and the like. A typical support is the OHP transparent filmdescribed above.

For production of an image projection sheet according to the invention,it is necessary to position the laminate film of the invention on theimage-formed adherend, such as an OHP transparent film, beforelamination. The positioning operation for conventional laminate filmshas been associated with serious difficulties. In the case of theinventive laminate film its fine structured surface allows the laminatefilm to be shifted across the surface of the adherend until pressure isapplied, causing the adhesive to wet the surface of the adherend. Anappropriate level of pressure and the resultant wetting produce asatisfactory bond between the adhesive and the adherend.

Also, by firmly pressing the laminate film against the adherend it ispossible to expel air confined in the continuous grooves out to theperiphery of the film, thereby eliminating air bubbles. Because the finecontinuous grooves and protrusions of the laminate film undergosubstantially complete crushing and the fine particles become buried inthe adhesive layer after the film is attached to the adherend, theamount of adhesive in contact with the adherend may be increased. Thisensures that the laminate film of the invention will have the desiredlevel of adhesion for the adherend.

EXAMPLES

The following examples are provided to illustrate different embodimentsand details of the invention. Although the examples serve this purpose,the particular ingredients and amounts used as well as other conditionsand details are not to be construed in a manner that would unduly limitthe scope of this invention. Unless otherwise specified, all parts areby weight.

Example 1

An image covering laminate film with an adhesive layer was fabricatedand used to make a laminated transparency sheet for an OHP as explainedabove with reference to FIG. 13. A perforated strip for filing was alsoprovided in the laminated transparency sheet.

An OHP transparent film was made using a color laser printer film,commercially available as Product No. CG3700 by Sumitomo 3M Co. Thetransparent film was loaded in a color laser printer (Color Laser ShotLBP-2040 by Canon, Inc.) for color image printing to fabricate a fullcolor transparency sheet.

Separately, a polyethylene terephthalate (PET) film (Lumirror 50T-60,product of Toray Co., Ltd.) was prepared as a transparent film basematerial to make an image covering laminate film. A polycoat liner(commercially available from Rexam Co.) made by polyethylene coating andsilicone treating a PET base material was made as a release liner. Amaster tool having a surface with a fine uneven structure of shape anddimensions corresponding to the desired fine uneven structure of theadhesive layer of the laminate film was used to emboss one side of therelease liner. This step produced a release liner having an unevensurface corresponding to the fine uneven structure of the master tool.The uneven structure of the release liner corresponds to and is exactlyopposite to the fine uneven structure (regular pyramidal structure) tobe formed on the surface of the adhesive layer fabricated in thisexample.

After mixing 100 parts of isooctyl acrylate (3M Co.) and 0.04 part of2,2-dimethoxy-1,2-diphenylethan-1-one (IRGACURE 651, trade name of CibaSpecialty Chemicals Co., Ltd.), the mixed solution was irradiated withultraviolet rays in a nitrogen atmosphere for partialphotopolymerization. To the resulting syrup, which had a coatableviscosity, was added 0.2 part of 2,2-dimethoxy-1,2-diphenylethan-1-oneand 0.2 part of 1,6-hexanediol diacrylate (KS-HDDA, trade name of NipponKayaku Co., Ltd.). The obtained syrup was coated at a thickness of 75 μmbetween one side of the film base material prepared in the previous stepand the uneven structure-bearing side of the release liner. The coatedsolution was irradiated with ultraviolet rays to complete thephotopolymerization. Hardening of the syrup produced a laminate filmwith an adhesive layer having the structure described above withreference to FIG. 1. The surface of the adhesive layer of the resultinglaminate film had a regular pyramidal uneven structure. The size of theuneven structure was as follows, based on FIG. 2. Pitch p betweenprotrusions: 197 μm; height h of protrusions from bottoms of continuousgrooves: 13 μm.

Also, a 16 mm wide storage strip (ET film) with small filing holes wasattached and fixed to one edge of the film base material of the laminatefilm using clear tape (Scotch600, commercially available from Sumitomo3M Co.).

After releasing the release liner from the strip-attached laminate filmit was attached to the toner image-bearing side of a previouslyfabricated transparency sheet via the adhesive layer. The laminate filmwas attached by hand lamination, but a rubber roller with a width of 47mm and a diameter of 40 mm was used for light pressing to contact bondthe laminate film to the transparency sheet. This produced an OHPlaminated transparency sheet with the cross-sectional structuredescribed above with reference to FIG. 13. Because of the good airremovability of this laminated transparency sheet, there were no defectsdue to residual air and produced a high quality projected color image.The perforated strip of the laminated transparency sheet was used foreasy filing in a binder.

Evaluation of Color Image Quality

For evaluation of the color image quality, laminated transparency sheetswere made by the same procedure as above, except for forming monochrome(yellow, magenta, cyan, red, green and blue) toner images instead of afull color image.

The Q factor of each of the laminated transparency sheets was measuredusing a haze meter (TC-HIII, trade name of,Tokyo Denshoku Co., Ltd.).Because the toner image of a transparency sheet usually results in ahigh level of light scattering and because such light scatteringproduces turbidity or clouding of the color of the projected image,measurement of the Q factor is especially useful for evaluation of thetransparency sheet image quality. The Q factor can be very accuratelymeasured by the ratio of the light scattering with respect to thetransmitted light (light contributing to the color image formation). TheQ factor is defined by the following formula.Q factor={(light attenuation due to absorption)+(light attenuation dueto scattering)}/(light attenuation due to absorption)

In the above formula, the lower limit for the Q factor is 1. Thisrepresents a case in which the light attenuation due to light scatteringis zero. A smaller Q factor indicates improved transparency of theprojected image.

Table 1 below contains a summary of the measurement results for the Qfactors of the laminated transparency sheets. The “Prior art” listed inTable 1 for comparison is a transparency sheet having a monochrome tonerimage formed by the same procedure described above on a conventional OHPtransparent film.

TABLE 1 Q factor Yellow Magenta Cyan Red Green Blue Laminated 12.9 1.41.5 1.8 2.5 1.3 transparency sheet (Present invention) Prior art >1002.8 4.2 3.0 5.0 2.9

The measurement results in Table 1 indicate that each of the laminatedtransparency sheets having the laminate film fabricated for this exampleattached to the image-bearing side exhibited a small Q factor forprojection of color images, or in other words, had high lighttransmittance. The laminate film of the invention can therefore providecolor images with excellent light transparency.

Example 2

1. Fabrication of Transparency Sheet

The “CG3700” color laser printer film used in Example 1 was prepared asan OHP transparent film. The transparent film was loaded into a colorlaser printer (Color LaserJet 4500, Hewlett-Packard) for monochrome(red, green, blue, yellow, magenta and cyan) color image printing tofabricate a total of 6 different transparency sheets.

Next, the light transmittance (%) of the red, green, blue and yellowcolor image-bearing transparency sheets was measured in a wavelengthrange of 380-820 nm. The light transmittance was measured using a #62601UV-Viscosity spectrophotometer by SMMD Analytical Laboratory Co., Ltd.The results of a series of measurements were plotted as shown in FIGS.14 to 17, and the averaged and summarized measurement results shown inTable 2 were obtained. In each of these graphs, CR is the red imagetransparency sheet, CG is the green image transparency sheet, CB is theblue image transparency sheet and CY is the yellow image transparencysheet. (C stands for “comparison”).

The haze values (%) and diffuse reflection values (%, average values forwavelengths of 380-720 nm) for the red, green, blue and yellow colorimage-bearing transparency sheets were measured using a BYK-Gardner TCSPlus spectrophotometer, giving the measurement results listed in Table 3below.

2. Fabrication of Laminate Film

An image covering laminate film was fabricated according to the sameprocedure as Example 1. For this example, however, the polyethyleneterephthalate (PET) film used was one by 3M Co., and the unevenstructure was formed in the following manner.

After mixing 90 parts of n-butyl acrylate (Aldrich Co.) and 10 parts of2-ethylhexyl acrylate (Aldrich Co.), the obtained mixed solution wasirradiated with ultraviolet rays in a nitrogen atmosphere for partialphotopolymerization. The obtained syrup was coated to a thickness of 3mils (76 μm) between one side of the film base material prepared in theprevious step and the uneven structure-bearing side of the releaseliner, and irradiated with ultraviolet rays to complete thephotopolymerization. The surface of the adhesive layer of the resultinglaminate film had a regular pyramidal uneven structure. The size of theuneven structure was as follows, based on FIG. 2. Pitch p betweenprotrusions: 197 μm; height h of protrusions from bottoms of continuousgrooves: 13 μm.

3. Fabrication of Laminated Transparency Sheet

After releasing the release liner from the laminate film, it wasattached to the toner image-bearing side of a previously fabricatedtransparency sheet via the adhesive layer. No pressure was applied yetat this stage, but hand lamination was done using a rubber roller with awidth of 47 mm and a diameter of 40 mm. The rubber roller was lightlypressed from left to right, top to bottom and center to outside. Thisproduced an OHP laminated transparency sheet with the laminate filmcontact bonded to the toner image side. Because of the satisfactory airremovability of this laminated transparency sheet, there were no defectsdue to residual air and produced a high quality projected color image.

4. Measurement of Light Transmittance Haze Value and Diffuse Reflectionof Laminated Transparency Sheet

The light transmittance (%) of the red, green, blue and yellow colorimage-bearing laminated transparencies fabricated in 3. above wasmeasured in a wavelength range of 380-820 nm in the same manner as 1.above, and upon plotting the data as shown in FIGS. 14 to 17, theaveraged and summarized measurement results shown in Table 2 wereobtained. In each of these graphs, R is the red image laminatedtransparency sheet, G is the green image laminated transparency sheet, Bis the blue image laminated transparency sheet and Y is the yellow imagelaminated transparency sheet.

The haze values (%) and diffuse reflection values (%, average values forwavelengths of 380-720 nm) for the red, green, blue and yellow colorimage-bearing laminated transparency sheets were measured using aBYK-Gardner TCS Plus spectrophotometer, giving the measurement resultslisted in Table 3 below.

TABLE 2 Transmittance (%, average value for 380-820 nm) Red Green BlueYellow Laminated 35.09 12.39 17.33 54.52 transparency sheet (Presentinvention) Prior art 17.43 5.71 6.28 19.96

TABLE 3 Diffuse reflection Haze value (%) (%, average value for 380-720nm) Red Green Blue Yellow Red Green Blue Yellow Laminated 67.5 76.1 43.557.0 4.55 2.03 2.36 5.21 transparency sheet (Present invention) Priorart 78.2 94.6 63.8 90.7 6.97 4.58 4.68 8.21

The measurement results in Tables 2 and 3 indicate that each of thelaminated transparency sheets having the laminate film fabricated forthis example attached to the image-bearing side exhibits superior lighttransmittance and can prevent haze and diffuse reflection, and thereforeallows projection of color images with notably higher quality comparedto a conventional transparency sheet with no laminate film.

5. Evaluation of Color Image Quality

For evaluation of the color image quality, the Q values of cyan, magentaand yellow color image-bearing laminated transparency sheets fabricatedby the same procedure as above and a corresponding transparency sheet(prior art) without a covering laminate film, fabricated for comparison,were measured using a haze meter (TC-HIII, trade name of Tokyo DenshokuCo., Ltd.), by the same procedure as in Example 1.

Table 4 below contains a summary of the measurement results for the Qfactors of the laminated transparency sheets.

TABLE 4 Q factor Cyan Magenta Yellow Laminated 1.6 1.5 6.7 transparencysheet (Present invention) Prior art 3.1 1.9 13.8

The measurement results in Table 4 indicate that each of the laminatedtransparency sheets having the laminate film fabricated for this exampleattached to the image-bearing side exhibited a small Q factor forprojection of color images, i.e., had high light transmittance. Thelaminate film of the invention can therefore provide color images withexcellent light transparency.

Example 3

An image covering laminate film provided with an adhesive layer such asexplained above with reference to FIG. 4 and FIG. 5 was made and usedfor making of a laminated transparency sheet for an OHP as explainedabove with reference to FIG. 13.

In the same manner as Example 1, a color laser printer film (Product No.CG3700 by Sumitomo 3M Co.) was loaded in a color laser printer (ColorLaser Shot LBP-2040 by Canon, Inc.) for printing to make a full colortransparency sheet.

Separately, a PET film (Lumirror 50T-60, trade name of Toray Co., Ltd.)was prepared in the same manner as Example 1, and a polycoat liner(commercially available from Rexam Co.) obtained by polyethylene coatingand silicone treatment of a PET base material was prepared as a releaseliner. A master tool having a surface with a group of fine protrusionsof shape and dimensions corresponding to the desired fine protrusions ofthe adhesive layer of the laminate film was then used for embossing oneside of the release liner. This produced a release liner having asurface with fine protrusions corresponding to the group of fineprotrusions of the master tool.

Next, a cluster of glass beads with a diameter of about 5 to 30 μm(commercially available as “Expancel” by Nobel Industries Co. of Sweden)was packed into the depressions formed on the release liner. For packingthe glass beads, they were first dispersed in a cellulose resin toprepare a slurry solution. The slurry solution then was applied onto oneside with a screen coater. The excess beads were scraped off with adoctor blade.

A fine uneven structure was then formed in the surface of the releaseliner by reembossing. The re-embossing was carried out in the samemanner as the previous step. The fine uneven structure formed here had ashape and dimensions corresponding to the intended fine uneven structureof the adhesive layer of the laminate film.

After mixing 93.5 parts of isooctyl acrylate (3M Co.), 6.5 parts ofacrylic acid (Wako Junyaku Industries) and 0.04 part of2,2-dimethoxy-1,2-diphenylethan-1-one (IRGACURE 651, trade name of ChibaSpecialty Chemicals Co., Ltd.), the mixed solution was irradiated withultraviolet rays in a nitrogen atmosphere for partialphotopolymerization. To this syrup there was further added 0.2 part of2,2-dimethoxy-1,2-diphenylethan-1-one. The obtained syrup was coated toa thickness of 75 μm between one side of the film base material preparedin the previous step and the uneven structure-bearing side of therelease liner, and was irradiated with ultraviolet rays to completephotopolymerization. Hardening of the syrup produced a laminate filmwith an adhesive layer having the structure described above withreference to FIG. 1. The surface of the adhesive layer of the resultinglaminate film had a regular pyramidal uneven structure and was packedwith glass beads. The size of the uneven structure was as follows, basedon FIG. 4. Pitch p₁ between protrusions: 197 μm; height h₁ ofprotrusions from bottoms of continuous grooves: 13 μm; pitch p₂ betweenglass beads 300 μm; and height h₂ of glass beads from bottoms ofcontinuous grooves: 20 μm.

After removing the release liner from the laminate film, it was attachedto the toner image-bearing side of a previously fabricated transparencysheet via the adhesive layer. The laminate film was attached by handlamination, but a rubber roller with a width of 47 mm and a diameter of40 mm was used for light pressing to contact bond the laminate film tothe transparency sheet. This produced an OHP laminated transparencysheet with the cross-sectional structure described above with referenceto FIG. 13. Because of the good air removability of this laminatedtransparency sheet, there were no defects due to residual air andproduced a high quality projected color image.

Evaluation of Color Image Quality

For evaluation of the color image quality, laminated transparency sheetswere fabricated by the same procedure as above, except for formingmonochrome (yellow, magenta, cyan, red, green and blue) toner imagesinstead of a full color image.

The Q factor of each of the laminated transparency sheets was measuredusing a haze meter (TC-HIII, trade name of Tokyo Denshoku Co., Ltd.), bythe same procedure as Example 1 above.

Table 5 below contains a summary of the measurement results for the Qfactors of the laminated transparency sheets. The “Prior art” listed inTable 5 is a transparency sheet having a monochrome toner image formedby the same procedure described above on a conventional OHP transparentfilm.

Example 4

The method described in Example 3 above was repeated, but for thisexample the adhesive layer was formed in the following manner.

A mixed solution of 100 parts of butyl acrylate (Mitsubishi ChemicalCo.) and 0.04 part of 2,2-dimethoxy-1,2-diphenylethan-1-one (IRGACURE651, trade name of Chiba Specialty Chemicals Co., Ltd.) was UVirradiated in a nitrogen atmosphere for partial photopolymerization, toprepare a coatable syrup.

To this syrup there were added 0.2 part of2,2-dimethoxy-1,2-diphenylethan-1-one and 0.1 part of 1,6-hexanedioldiacrylate (KS-HDDA, trade name of Nippon Kayaku Co., Ltd.). The syrupwas used to fabricate a laminate film in the same manner as Example 3.

Because of the good air removability of the resulting OHP laminatedtransparency sheet, there were no defects due to residual air andproduced a high quality projected color image.

Next, for evaluation of the color image quality, the same methoddescribed in Example 3 above was repeated to fabricate laminatedtransparency sheets. The Q factor of each of the laminated transparencysheets was measured using a haze meter (TC-HIII, trade name of TokyoDenshoku Co., Ltd.), giving the measurement results shown in Table 5below.

TABLE 5 Q factor Yellow Magenta Cyan Red Green Blue Example 3 16.7 1.41.5 1.8 2.7 1.3 Example 4 15.7 1.4 1.4 1.7 2.5 1.3 Prior art >100 2.84.4 3.0 5.2 2.9

The measurement results in Table 5 indicate that each of the laminatedtransparency sheets having the laminate film fabricated in Examples 3and 4 attached to the image-bearing side exhibited a small Q factor forprojection of color images, Le., had high light transmittance. Thelaminate film of the invention can therefore provide color images withexcellent light transparency.

Example 5

For this example, an OHP laminated transparency sheet was produced inthe same manner as Example 3 above except for using an image coveringlaminate film provided with an adhesive layer such as explained abovewith reference to FIG. 8.

The image covering laminate film was fabricated in the following manner.

First, a mixed solution of 100 parts of isooctyl acrylate (3M Co.) and0.04 part of 2,2-dimethoxy-1,2-diphenylethan-1-one (IRGACURE 651, tradename of Chiba Specialty Chemicals Co., Ltd.) was UV irradiated in anitrogen atmosphere for partial photopolymerization, to prepare acoatable syrup.

To this syrup there were added 0.2 part of2,2-dimethoxy-1,2-diphenylethan-1-one and 0.25 part of 1,6-hexanedioldiacrylate (KS-HDDA, trade name of Nippon Kayaku Co., Ltd.). An adhesivelayer was formed from the syrup by the same method as Example 1. Forthis example, the syrup was coated between a PET liner as thetransparent film base material and a Polyslick liner (commerciallyavailable from Inncoat Co.) as the release liner. When the adhesivelayer was UV irradiated for photopolymerization, it exhibited a finestructure on its surface with the following dimensions based on FIG. 8:Pitch p=197 μm, height h=10 μm, continuous groove bottom width d₁=3 μm,continuous groove top width d₂=15 μm.

After removing the release liner from the laminate film, it was handlaminated onto the color image of an OHP transparent film. The resultingOHP laminated transparency sheet had no defects due to residual air, andproduced a high quality projected color image.

Measurement of the Q factor of the obtained color image gave the resultsshown in Table 6 below.

Example 6

For this example, an OHP laminated transparency sheet was produced inthe same manner as Example 3 above except for using an image coveringlaminate film provided with an adhesive layer such as explained abovewith reference to FIG. 10.

The image covering laminate film was fabricated in the following manner.

First, a mixed solution of 100 parts of isooctyl acrylate (3M Co.) and0.04 part of 2,2-dimethoxy-1,2-diphenylethan-1-one (IRGACURE 651, tradename of Chiba Specialty Chemicals Co., Ltd.) was UV irradiated in anitrogen atmosphere for partial photopolymerization, to prepare acoatable syrup.

To this syrup were added 0.2 part of2,2-dimethoxy-1,2-diphenylethan-1-one and 0.15 part of 1,6-hexanedioldiacrylate (KS-HDDA, trade name of Nippon Kayaku Co., Ltd.). An adhesivelayer was formed from the syrup by the same method as Example 1. Forthis example, the syrup was coated between a PET liner as thetransparent film base material and a Polyslick liner (commerciallyavailable from Inncoat Co.) as the release liner. When the adhesivelayer was then UV irradiated for photopolymerization, the adhesive layerexhibited a fine structure on its surface with the following dimensionsbased on FIG. 10: Pitch p=197 μm, height h₁=15 μm, height h₂=10 μm,continuous groove bottom width d₁=3 μm, continuous groove top widthd₂=20 μm, double mechanism base length d₃=38 μm.

After removing the release liner from the laminate film, it was handlaminated onto the color image of an OHP transparent film. The resultingOHP laminated transparency sheet had no defects due to residual air, andproduced a high quality projected color-image.

Measurement of the Q factor of the obtained color image gave the resultsshown in Table 6 below.

TABLE 6 Q factor Yellow Magenta Cyan Red Green Blue Example 5 5.4 1.41.4 1.6 2.5 1.4 Example 6 5.6 1.4 1.4 1.6 2.4 1.3

The measurement results in Table 6 indicate that the color imagestreated with the laminate films obtained in Examples 5 and 6 had small Qfactors (i.e., high light transparency). These laminate films of theinvention can therefore provide color images with excellent lighttransparency.

As explained above, a laminate film according to the invention can beused without capturing and incorporating air as air bubbles under theadhesive layer during application onto adherends. In cases where airbubbles are present, it allows them to be easily removed by theattachment procedure (i.e., the air removability is satisfactory). Thefine continuous grooves in the adhesive layer used for expelling airbubbles is eliminated after lamination, so that there is no adverseeffect on light scattering.

Furthermore, because the laminate film of the invention exhibits evenbetter slidability on the surface of adherends by the action of fineparticles loaded therein, it is possible to achieve easier and moreaccurate positioning and attachment operations.

According to the invention, therefore, when laminating and attachingonto OHP transparent films, the toner image surface is flattened toreduce scattering of transmitted light, thereby allowing enhancement ofimage quality. It also allows for hand lamination at room temperaturewithout the need for special lamination equipment or skills. Theattachment manageability and especially the positionability, slidabllityand air removability of the inventive laminate film are all satisfactoryand reattachment can be carried out if necessary.

According to the invention there may be provided image covering laminatefilms that can improve the storage and filing properties of OHPtransparency sheets.

According to the invention there may also be provided image projectionsheets with excellent quality of projected images and superiorhandleability and storage properties.

1. An image covering laminate film for covering of an image carried by asupport, comprising: a transparent base material; and a transparentadhesive layer formed on one side of the base material, and wherein saidadhesive layer is composed of a pressure-sensitive adhesive and has asurface with a fine uneven structure containing non-adhesive fineparticles, wherein said uneven structure of the surface of said adhesivelayer defines continuous grooves configured to expel air trapped betweensaid laminate film and the image-bearing side of said support when thelaminate film is attached to the image-bearing side of said support, andwherein the uneven structure itself has a shape and dimensions allowingit to be incorporated into said adhesive layer and to disappear once theattachment is complete.
 2. An image covering laminate film according toclaim 1, characterized in that said fine particles are glass beads. 3.An image covering laminate film according to claim 1, characterized bybeing further provided with a release liner covering said adhesivelayer.
 4. An image covering laminate film according to claim 1,characterized in that said laminate film further includes a strip whichextends out at a prescribed length from the edge.
 5. An image coveringlaminate film according to claim 1, characterized in that said supportis a transparent plastic film with a toner image fusion bonded to itssurface.
 6. An image projection sheet comprising (a) a transparentsupport, (b) a toner image carried on the surface of the support, and(c) the laminate film of claim 1, wherein said adhesive layer of saidlaminate film is disposed on said toner image.
 7. An image projectionsheet according to claim 6, characterized in that said laminate filmfurther includes a strip which extends out at a prescribed length fromthe edge.
 8. An image projection sheet according to claim 6,characterized in that it is used for an overhead projector.
 9. An imagecovering laminate film according to claim 1, characterized in that theuneven structure of the surface of said adhesive layer defines a doublemechanism structure.
 10. An image covering laminate film according toclaim 9, characterized in that the double mechanism structure comprisesa first structure having a first surface, and a second structurepositioned on the first surface.